Practical design and application of Light Emitting Diodes (LED) type devices for use in Area Lighting and like schemes are limited by thermal energy-management issues. Therefore, by producing more light intensive LEDs more thermal energy is produced in the same unit volume of the device. Practical design of a LED light aims at finding the passive point and the optimal balance between the light output versus the entropy.
It is known that LEDs exhibit negative temperature coefficient aspects, at fixed power input, as the device's operating heat rises (entropy), the device's light output decreases. It is the entropy inside the LED chip and the semiconductors accompanied with it that determines the degradation level of the LED.
Attempts have been made in the prior art to solve the negative temperature coefficient issues. As an example, in LED highway traffic signal devices housings with ventilation configurations, both of passive (convection-type) and active (fan-driven-type) have been provided to prevent the LED-s from overheating. Present art LED traffic signal devices also address the inherent negative temperature coefficient nature via the electrical power supply. These approaches either increase power to the device to compensate for light output loss or address the form of the provided electrical power such as sine vs. square wave in an attempt to moderate the entropy. According to prior art, entropy in a closed system; as LEDs, will continue to increase until the LED no longer produces any light. All passive systems show similar development. The higher the current, the bigger portion of the power consumed becomes entropy. Entropy can not decrease in any system but it can at best, be constant.
This is only possible in active cooling systems, where external work is needed to keep the entropy inside the system at acceptable levels.
Solid state thermoelectric modules (TEM) also referred to as thermoelectric coolers (TEC) or heat pumps have been used in various applications since the introduction of semiconductor thermocouple materials. Such devices convert electrical energy into a temperature gradient, known as the “Peltier” effect or convert thermal energy from a temperature gradient into electrical energy. By applying a current through a TEM a temperature gradient is created and heat is transferred from one side, the “cold” side of the TEM to the other side, the “hot” side.
TEMs have been considered unsuitable for cooling LED lighting devices as they have been ruled out for insufficient efficiency; that is, if configured and operated with conventional settings the energy cost of operating a TEM for cooling an LED device is more than the energy gained in operating the LED at a reduced current and a slower entropy incensement's.
There is thus a need for providing an improved LED system that overcomes the above mentioned drawbacks.